This project deals with the dissection and manipulation of protein structure. Alanine +RNA synthetase is to be used for these purposes. Fragments of the enzyme are to be produced in quantity and subjected to crystallization attempts. These fragments are know to encode specific functional domains. A major emphasis is placed on isolation and characterization of a small fragment that interacts with +RNA. Synthesis of polypeptides that encompass a putative +RNA binding domain will be attempted. Other studies focus on the manipulation of the alanine +RNA synthetase structure so as to achieve higher catalytic power and greater ligand affinities. Preliminary work has been done on a selected system for isolation of enzyme molecules with enhanced properties. This system will be explored for the isolation of protein in variants.